Method of providing feedback to a media server in a wireless communication system

ABSTRACT

The present invention provides a method involving a media server, a wireless network, and at least one media client associated with at least one air interface with the wireless network. The method includes accessing first information indicative of at least one state of the at least one media client. The first information is provided by the at least one media client. The method also includes accessing second information indicative of resources associated with the at least one air interface. The second information is provided by the wireless network. The method further includes providing at least one feedback parameter to the media server. The at least one feedback parameter is formed based on the first and second information.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to communication systems, and, moreparticularly, to wireless communication systems.

2. Description of the Related Art

Streaming media services (e.g. music, video) over wireless communicationnetworks have been gaining in popularity, and are likely to becomecommercially important to wireless service providers in the near future.A major impediment to their success is the often poor and/or unreliableaudio or video quality associated with these services. Packetstransmitted through the wireless communication network may be lost,delayed, or experience jitter. For example, signal strength fluctuationsdue to environmental changes and the need to share the wireless accessmedium among multiple users lead to significant fluctuations in the rateat which packets carrying a media stream are delivered to mobile unitsand/or the applications running on the mobile unit such as a mediaplayer. Packets may also be lost as they traverse the air interface fromthe media server to the client, which may cause interruptions in themedia service and/or degraded quality of the media service. Conventionalmedia sessions attempt to reduce the effects of lost packets, delayedpackets, and/or jitter by buffering the received data stream.

FIG. 1 conceptually illustrates one exemplary embodiment of aconventional system 100 for streaming media over a wireless network 105.In the illustrated embodiment, the system 100 includes a media server110 that streams media over the wireless network 105 to at least oneclient 115, such as a mobile unit or an application running on themobile unit. The media server 110 includes a media encoder 120 thatencodes a signal representative of the media that is being streamed tothe client 115. The media encoder 120 is capable of encoding streamingmedia at one or more average bit rates, referred to as hereafter asencoding rates. Typically, for a given media, a higher encoding rate isassociated with better media quality from the end-user's perspective.Moreover, even for a given encoding rate (which refers to the averagebit-rate at the output of the encoder), the actual bit rate at theoutput of the encoder can vary substantially over time depending on thecorresponding media content. For example, relatively high bit rates maybe observed during image sequences that include substantial motion orhave a high degree of detail, whereas relatively low bit rates may beobserved during static images.

Plots 125(1-n) show the cumulative encoded bytes (vertical axis inarbitrary units) at the output of the media encoder 120 as a function oftime (horizontal axis in arbitrary units) for different encoding rates.The encoding rate corresponds to the average slope of the correspondingplot. Plots 125(1-n) clearly point out the differences in the variousencoding rates the media encoder 120 is capable of outputting. Moreover,as illustrated by plots 125(1-n), for each encoding rate, theinstantaneous bit rate at the output of the media encoder 120,represented by the slope of the corresponding curve as a function oftime, can be seen to vary a great deal over time. As explained earlier,if an image in a video stream includes a relatively large percentage ofregions that are in motion or have a high degree of detail, then thenumber of bytes at the output of the media encoder 120 may increase,resulting in a high (instantaneous) bit rate. However, if the image inthe video stream changes so that the percentage of regions that are inmotion or have a high degree of detail decreases, then the number ofbytes at the output of the media encoder 120 may decrease resulting in alow (instantaneous) bit rate. The media server 110 may therefore includea rate shaping element 130 to provide an approximately constant numberof transmitted bytes per unit time to the wireless network 105, asindicated by the plot 135.

The wireless network 105 typically performs scheduling of the packetsthat are transmitted over the air interface to the client 115, as wellas implementing adaptive modulation and coding of the packets andautomatic repeat request functionality. However, as discussed above, thepackets transmitted by the wireless network 105 may be lost, delayed,and/or jittery. Consequently, the number of bytes per unit time that areprovided to the client 115 may vary over time, as indicated by the plot140. In the illustrated embodiment, the client 115 includes a de-jitterbuffer 145 and a pre-decoder buffer 150 to attempt to compensate forlost packets, delayed packets, and/or jittery packet arrival times. Forexample, packets received by the client 115 may be stored in thede-jitter buffer 145 and then pushed out of the de-jitter buffer 145 atan approximately constant number of bytes per unit time, as indicated bythe plot 155. The pre-decoder buffer 150 may receive the data streamprovided by the de-jitter buffer 145 and may provide the receivedpackets to a media decoder 160 at a desired number of bytes per unittime, as indicated by the plot 165.

The media server 110 and the client 115 include built-in features thatallow the client 115 to send intermittent feedback to the media server110, as indicated by the arrow 170. The feedback 170 typically informsthe media server 110 of end-to-end performance metrics such as the rateat which packets are being delivered, loss of packets, available bufferspace, and the like. The end-to-end performance metrics are used inconjunction with information local to the media server 110 to controlthe source encoding rate and/or transmission rate. However, end-to-endperformance metrics only provide information that can be deduced fromthe data stream received by the client 115. Furthermore, at least inpart to reduce overhead that must be transmitted over limited uplinkbandwidth available for streaming media sessions, the client 115typically provides the feedback 170 on a relatively long time scale.e.g. every 3-5 seconds.

The lack of direct knowledge of network conditions and/or the effects ofcompeting users, as well as the long time scale, limits the usefulnessof the feedback 170. For example, the wireless network 105 typicallyimplements scheduling and rate adaptation techniques based on fastchannel quality feedback over the wireless link in order to exploitmulti-user diversity resulting from fast variations (e.g., on the scaleof milliseconds) in channel quality. These techniques result insignificant variability in the rate achieved across the wireless linkfor a given media session, and the feedback 170 is not provided to themedia server 110 often enough to help it effectively respond to rapidvariations in the supported transmission rate. As a result, theconventional media server 110 cannot deliver the best possible mediaquality in the presence of rapid variations in the transmission rateover the air interface. Furthermore, the feedback 170 does not includeinformation that provides direct knowledge of network conditions andusers competing for the shared bandwidth, which precludes thepossibility of the media server 110 employing more sophisticated methodsto predict buffer overflows and underflows, which can help the server110 take proactive actions to avoid these events.

Since the media server 1 10 can only shape transmission rates based uponthe relatively slow end-to-end feedback 170, the resources that areavailable for streaming media over the wireless network 105 may not beused in an optimal or efficient manner. For example, the media server110 typically selects a transmission rate based on the feedback 170. Theselected transmission rate may reflect the effects of averagingconditions in the wireless network 105 over a relatively long period oftime. However, the actual transmission rates that are supported by thewireless network 105 at any given moment may vary widely from thisaverage rate, resulting in an inefficient use of the resources. If theaverage values are used to select a high media source encoding rate thatis not sustainable during the time period that packets are transmittedat this rate, packet losses may occur, resulting in unacceptable mediaquality; also, downlink resource availability for other users orsessions may be undesirably reduced. On the other hand, selecting lowersource rates may underutilize the available resources during periodswhen the wireless network could support higher transmission rates.Under-utilization of the available resources may mean delivering themedia at less than the best possible quality level under prevailingconditions.

SUMMARY OF THE INVENTION

The present invention is directed to addressing the effects of one ormore of the problems set forth above. The following presents asimplified summary of the invention in order to provide a basicunderstanding of some aspects of the invention. This summary is not anexhaustive overview of the invention. It is not intended to identify keyor critical elements of the invention or to delineate the scope of theinvention. Its sole purpose is to present some concepts in a simplifiedform as a prelude to the more detailed description that is discussedlater.

In one embodiment of the present invention, a method is providedinvolving a media server, a wireless network, and at least one mediaclient associated with at least one air interface with the wirelessnetwork. The method includes accessing first information indicative ofat least one state of the at least one media client. The firstinformation is provided by the at least one media client. The methodalso includes accessing second information indicative of resourcesassociated with the at least one air interface. The second informationis provided by the wireless network. The method further includesproviding at least one feedback parameter to the media server. The atleast one feedback parameter is formed based on the first and secondinformation.

In another embodiment of the present invention, a method is providedinvolving a media server, a wireless network, and at least one mediaclient associated with at least one air interface with the wirelessnetwork. The method includes receiving at least one feedback parameterat the media server. The at least one feedback parameter is formed basedon first information indicative of at least one state of the at leastone media client and second information indicative of resourcesassociated with the at least one air interface. The first information isprovided by the at least one media client and the second information isprovided by the wireless network. The method also includes providing atleast one packet at a rate determined based on the at least one feedbackparameter.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be understood by reference to the followingdescription taken in conjunction with the accompanying drawings, inwhich like reference numerals identify like elements, and in which:

FIG. 1 conceptually illustrates one exemplary embodiment of aconventional system for streaming media over a wireless network;

FIG. 2 conceptually illustrates a first exemplary embodiment of a systemfor streaming media over a wireless network, in accordance with thepresent invention; and

FIG. 3 conceptually illustrates a second exemplary embodiment of asystem for streaming media over a wireless network, in accordance withthe present invention.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof have been shown by wayof example in the drawings and are herein described in detail. It shouldbe understood, however, that the description herein of specificembodiments is not intended to limit the invention to the particularforms disclosed, but on the contrary, the intention is to cover allmodifications, equivalents, and alternatives falling within the scope ofthe invention as defined by the appended claims.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Illustrative embodiments of the invention are described below. In theinterest of clarity, not all features of an actual implementation aredescribed in this specification. It will of course be appreciated thatin the development of any such actual embodiment, numerousimplementation-specific decisions should be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming, but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure.

Portions of the present invention and corresponding detailed descriptionare presented in terms of software, or algorithms and symbolicrepresentations of operations on data bits within a computer memory.These descriptions and representations are the ones by which those ofordinary skill in the art effectively convey the substance of their workto others of ordinary skill in the art. An algorithm, as the term isused here, and as it is used generally, is conceived to be aself-consistent sequence of steps leading to a desired result. The stepsare those requiring physical manipulations of physical quantities.Usually, though not necessarily, these quantities take the form ofoptical, electrical, or magnetic signals capable of being stored,transferred, combined, compared, and otherwise manipulated. It hasproven convenient at times, principally for reasons of common usage, torefer to these signals as bits, values, elements, symbols, characters,terms, numbers, or the like.

It should be borne in mind, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities. Unlessspecifically stated otherwise, or as is apparent from the discussion,terms such as “processing” or “computing” or “calculating” or“determining” or “displaying” or the like, refer to the action andprocesses of a computer system, or similar electronic computing device,that manipulates and transforms data represented as physical, electronicquantities within the computer system's registers and memories intoother data similarly represented as physical quantities within thecomputer system memories or registers or other such information storage,transmission or display devices.

Note also that the software implemented aspects of the invention aretypically encoded on some form of program storage medium or implementedover some type of transmission medium. The program storage medium may bemagnetic (e.g., a floppy disk or a hard drive) or optical (e.g., acompact disk read only memory, or “CD ROM”), and may be read only orrandom access. Similarly, the transmission medium may be twisted wirepairs, coaxial cable, optical fiber, or some other suitable transmissionmedium known to the art. The invention is not limited by these aspectsof any given implementation.

The present invention will now be described with reference to theattached figures. Various structures, systems and devices areschematically depicted in the drawings for purposes of explanation onlyand so as to not obscure the present invention with details that arewell known to those skilled in the art. Nevertheless, the attacheddrawings are included to describe and explain illustrative examples ofthe present invention. The words and phrases used herein should beunderstood and interpreted to have a meaning consistent with theunderstanding of those words and phrases by those skilled in therelevant art. No special definition of a term or phrase, i.e., adefinition that is different from the ordinary and customary meaning asunderstood by those skilled in the art, is intended to be implied byconsistent usage of the term or phrase herein. To the extent that a termor phrase is intended to have a special meaning, i.e., a meaning otherthan that understood by skilled artisans, such a special definition willbe expressly set forth in the specification in a definitional mannerthat directly and unequivocally provides the special definition for theterm or phrase.

FIG. 2 conceptually illustrates a first exemplary embodiment of a system200 for streaming media over a wireless network 205. In the illustratedembodiment, the system 200 includes a media server 210 that streamsmedia over the wireless network 205 to at least one client 215, such asa mobile unit or an application running on the mobile unit. The wirelessnetwork 205, the media server 210, and the client 215 may operateaccording to the Universal Mobile Telecommunication System (UMTS)standards and/or protocols. For example, in streaming media sessions,the Real-time Transport Protocol (RTP) may be used to carry the mediacontent and the associated Real Time Control Protocol (RTCP) may be usedto carry the associated control packets. A third protocol, the Real TimeStreaming Protocol (RTSP), may be used for the transmission of messagesfor session setup (including capability exchange), teardown, and someuser actions (e.g. pause, fast-forward, etc.). Details regardingRTP/RTCP and RTSP can be found in the Internet Engineering Task ForceRequests for Comments (IETF RFCs) 1889 and 2326, respectively. However,persons of ordinary skill in the art having benefit of the presentdisclosure should appreciate that the first exemplary embodiment isintended to be illustrative and that the present invention is notlimited to these standards and/or protocols.

The media server 210 includes a media encoder 220 that encodes a signalrepresentative of the media that is being streamed to the client 215.The media encoder 220 is capable of delivering the media at one or moreencoding rates. Also, as described earlier, for each encoding rate, theactual instantaneous bit rate at the output of the media encoder 220varies with time depending on the media content. The encoded datastreams include information that may be used to represent audio, video,a combination thereof, or any other desirable media. In an alternativeembodiment, the media server 210 does not include the media encoder 220.Instead, the media encoder 220 is a separate device that encodes themedia at possibly different (encoding) rates. The media server 210stores the encoded media output produced by the media encoder 220 indifferent files and streams the media to client devices duringcorresponding media sessions by reading from the stored encoded mediafiles.

Plots 225(1-n) show cumulative encoded bytes (vertical axis in arbitraryunits) at the output of the media encoder 220 as a function of time(horizontal axis in arbitrary units) for different encoding rates. Asshown in plots 225(1-n), in each plot, the actual (instantaneous) bitrate, which corresponds to the slope of the corresponding plot, variesover time. For example, if an image in the corresponding video streamincludes a relatively large percentage of regions that are in motion orhave a high degree of detail, then the instantaneous bit rate at theoutput of the media encoder 220 may be high. However, if the image inthe video stream changes so that the percentage of regions that are inmotion or have a high degree of detail decreases, then the instantaneousbit rate at the output of the media encoder 220 may be low. The mediaserver 210 may therefore include a rate shaping element 230 to providean approximately steady output stream to the wireless network 205, asindicated by the plot 235. The target transmission rate used by the rateshaping element 230 may be selected based upon feedback from thewireless network 205 and/or the client 215, as will be discussed indetail below.

In the first exemplary embodiment, the client 215 includes a de-jitterbuffer 235 and a pre-decoder buffer 240 to attempt to compensate forlost packets, delayed packets, and/or jittery packet arrival times. Forexample, packets received by the client 215 may be stored in thede-jitter buffer 235 and then pushed out of the de-jitter buffer 240 atan approximately constant number of bytes per unit time, as indicated bythe plot 245. The pre-decoder buffer 240 may receive the data streamprovided by the de-jitter buffer 235 and may provide the receivedpackets to a media decoder 250 at a desired number of bytes per unittime, as indicated by the plot 255. However, persons of ordinary skillin the art having benefit of the present disclosure should appreciatethat a first exemplary embodiment of the client is intended to beillustrative and alternative embodiments of the client 215 may notinclude exactly the same number and/or structure of buffers 235, 240.

The wireless communication system 200 includes a signaling proxy 260. Inone embodiment, the signaling proxy 260 may be attached to a wirelessaccess network entity in the wireless network 205, such as a GatewayGPRS Support Node (GGSN) specified in the 3GPP Universal MobileTelecommunications System (UMTS) standard and/or a Packet Data ServingNode (PDSN) specified in the 3GPP2 cdma2000 standard. However, in otherembodiments of the invention it is possible to attach the signalingproxy to other access network entities such as a Serving GPRS SupportNode (SGSN), a Radio Network Controller (RNC), or, in the case of anaccess network comprising base-station routers that are characterized bya flat architecture (e.g. multiple functionalities handled by RNC, SGSNand GGSN collapsed into only one entity, the base-station router), tothe base-stations themselves. The signaling proxy 260 may be implementedin software, firmware, hardware, or any combination thereof.

The signaling proxy 260 receives feedback 265 from the client 215. Inone embodiment, the feedback 265 from the client 215 is indicative ofthe current session state of the client 215. For example, the signalingproxy 260 may intervene in the flow of RTCP and RTSP messages. Duringsession setup and teardown as well as during the lifetime of a session,control messages (e.g., RTCP and RTSP messages associated with the mediasession) generated by the client 215, which would normally go directlyto the media server 210 are, instead, provided to the signaling proxy260. These messages may help the signaling proxy 260 keep track of useractions as well as the state of the client 215 (e.g. buffer contents,expected time for overflow/underflow, etc.). In one embodiment, the RTPpackets carrying the media content may flow directly from the mediaserver 210 to the client 215.

The signaling proxy 260 also receives feedback 270 from the wirelessnetwork 205. In one embodiment, the feedback 270 from the wirelessnetwork 205 is indicative of resources associated with an air interfacebetween the wireless network 205 and the client 215. For example, thesignaling proxy 260 may receive fast feedback 270 in the form ofRAN-Proxy Control Packets from the sending Radio Link Control Protocolhandler, which may be implemented without loss of generality at theRadio Network Controller. In the case of a wireless access network withbase-station routers, the signaling proxy 260 may be attached to theserouters and the information concerning buffer levels, availablebandwidth, number of competing users, etc. will be locally available.The feedback 270 apprises the signaling proxy 260 of the detailed systeminformation and system view available from entities in the wirelessnetwork 205, such as buffer levels at the RNC, the number of userssharing the downlink bandwidth with the media session, the bandwidthavailable to each user and the like.

In various alternative embodiments, the feedback 265, 270 may either beprovided periodically and/or may be triggered by certain events. Forexample, the wireless network 205 may provide feedback 270 in responseto detecting changes in link quality metrics such as a signal tointerference plus noise ratio dropping below a certain threshold orrising above a certain threshold. For another example, the wirelessnetwork 205 may provide feedback 270 in response to detecting anincrease or a decrease in buffer levels.

The signaling proxy 260 uses the feedback 265, 270 to form controlinformation that may be provided to the media server 210, as indicatedby the arrow 275. In one embodiment, the signaling proxy 260 uses theinformation in the feedback 265, 270 respectively from the client 215and from the sending Radio Link Control Protocol entity or entities inthe wireless network 205 to generate a set of feedback parameters thatare signaled back to the media server 215. In one embodiment, thefeedback parameters are included in Proxy-Server Control Packets thatcan be carried using the existing protocols (e.g. RTCP) with suitableextensions to minimize changes to existing media servers and supportinginfrastructures. The feedback parameters may enhance the media server210's knowledge of conditions at the clients 215 and over the wirelessnetwork 205. In one embodiment, the control packets transmitted by thesignaling proxy 260 appear just like those generated by the client 215except that they now contain one or more additional parameters, such asthe maximum rate (for the corresponding media session) that can becurrently sustained in the wireless network 205, the amount of databelonging to the client 215 that is buffered at the RNC, the number ofRTP packets belonging to the client 215 that were delivered to theclient 215 over the previous feedback interval, and the like. The restof the contents of the Proxy-Server Control Packets may be preserved tocorrespond to existing state of the art set-ups, which are based eitheron the RTP-RTCP protocol or on proprietary protocols.

In the illustrated embodiment, the signaling proxy 260 may be coupled tothe wireless network 205 and/or the media server 210 by wiredconnections. The bandwidth constraints between the signaling proxy 260and the media server 210 are much weaker (relative to the client-serverchannel) when the signaling proxy 260 is hosted on the high bandwidth,wired side of the network 205. Consequently, the signaling proxy 260 cansend its control (feedback) packets to the media server 210 atsignificantly higher rates than would be possible if the client 215 andthe media server 210 directly exchanged control packets over the airinterface. This is a distinct advantage over the state-of-the art andmay have a direct and positive impact on the quality of mediaconnections as explained below.

In one embodiment, in the downlink direction, control information, suchas the RTCP and RTSP messages, transmitted by the media server 210 maybe passed on to the signaling proxy 260, which may then forward it tothe client device 215, with appropriate changes if needed. Thisarrangement helps the signaling proxy 260 determine the sessionparameters negotiated between the client 215 and the server 210 and tobe aware of what the expected service characteristics are from each oftheir viewpoints.

The capability of obtaining feedback information directly from the mediaclient combined with the comprehensive current knowledge of airlinkconditions and offered load from the RNC, puts the proxy 260 in a uniqueposition to intelligently influence the user-perceived quality ofend-to-end media transfers. Indeed, by using the information receivedfrom the client 215, as well as that received from the wireless network205, the signaling proxy 260 is in the right position to help the mediaserver 210 make accurate predictions about the likelihood of bufferoverflows and underflows if the media server 210 were to transmit thestream at different rates.

FIG. 3 conceptually illustrates a second exemplary embodiment of asystem 300 for streaming media over a wireless network. In theillustrated embodiment, consistent with the preceding description, theentire network between the media server 315 and the media client 310will be referred to as the wireless network. The network segment lyingbetween the media server 315 and the network element GGSN 320 will bereferred to as core network 305 and the network segment beginning withthe GGSN 320 and ending at the media client 310 will be referred to asthe wireless access network 327. In the illustrated embodiment, thewireless access network 327 including one or more base stations 307 isbased on the Universal Mobile Telecommunications System (UMTS) (3GPP)standard. However, the techniques described herein may also be appliedto any other wireless networking technology and standards, e.g.,cdma2000 High Rate Packet Data (HRPD) or IEEE 802.16e/WiMAX. In the caseof cdma2000 HRPD, for instance, system 300 would appear identical tothat in FIG. 3, except that the node pair, Serving GPRS Support Node(SGSN) 303 and the Gateway GPRS Support Node (GGSN) 320, are replaced bya single entity known as the Packet Data Serving Node (PDSN).Furthermore, although a hierarchical architecture is illustrated, thetechniques described herein may also be applied to flat-InternetProtocol (flat-IP) based architectures where Layer 3 routing (i.e., IP)and control functions relating to the wireless access network areperformed by the base station.

In the illustrated embodiment, a mobile client 310 initiates a streamingvideo session with a media server 315 over the wireless network 300. Forexample, the client 310 may request a streaming video session by sendingan RTSP message to the server 315. As this message reaches the GGSN 320,it forwards it to a signaling proxy 325 instead of the server 315. Theproxy 325 inspects this message, and realizing that it could be thebeginning of a new streaming video session, makes an entry into itslocal cache. It then forwards the message to the server 315. The server315 responds to the message and the subsequent RTSP messages exchangedby the client 310 and the server 315 to carry out “capability exchange”are also routed via the signaling proxy 325. This enables the proxy 325to discover the relevant session parameters (e.g. bandwidth, buffersize, etc.) agreed upon by the client 310 and the server 315. If thecapability exchange includes the rate or time interval at which theclient 310 is to send its receiver report to the server 315, the proxy325 modifies this parameter as it forwards the corresponding message tothe server 315 so that the server 315 is prepared to receive feedback atthe appropriate time interval or rate as determined by the proxy. Inaddition to regular reporting intervals, note that under certainconditions (e.g. changes in sustainable rate or buffer status at theRNC), the proxy 325 may also choose to autonomously send feedbackreports to the server 315. The modification enables the proxy 325 tosend reports to the server 315 at a much higher rate (consistent withthe abundant bandwidth available between the proxy 325 and the server315) while allowing the client 310 to send its reports (which areintercepted by the proxy 325) at a lower rate.

After the capability exchange with the server 315, the client 310initiates the establishment of a Packet Data Protocol (PDP) context anda Radio Access Bearer (RAB) to carry the streaming video session withthe desired Quality of Service over the downlink. When the RAB and thecorresponding Radio Bearer (RB) have been set up, a radio networkcontroller (RNC) 330 informs the signaling proxy 325 about the event. Ifthe proxy 325 already has an entry in its cache for a correspondingstreaming video session, it responds with a positive indication,instructing the RNC 330 to send periodic feedback (to the proxy 325)about the session's sustainable rate, buffer occupancy and the like. Ata minimum, this feedback should include the sustainable rate (i.e. themaximum transmission rate at which the session can stream under thecurrent conditions) for the session; the other parameters are optional.

From this point on, the RNC 330 begins to periodically report to thesignaling proxy 325 the streaming session's sustainable rate (and,possibly, the amount of data stored in the buffer assigned for thatsession by the RNC 330 and/or other relevant parameters). When theserver 315 starts streaming, RTP packets carrying the audio/videopayload associated with the streaming session begin to flow from theserver to the client 310 via the GGSN 320. In one embodiment, thesepackets are not routed via the signaling proxy 325. The client 310buffers up these packets for an amount of time known in the literatureas “pre-roll,” and then starts decoding and playing them out. When thisprocess begins at the client 310, the client 310 starts sending receiverreports to the server 315, informing the server 315 about one or moreparameters such as the amount of data received, the amount of data lost,identifier of the packet/frame to be played out next, and so on. In oneembodiment, these reports may be sent rather infrequently, at intervalsof a few seconds, such as once every 3-5 seconds.

The receiver reports transmitted by the client 310 may be carried inRTCP packets. The GGSN 320 forwards all RTCP packets received in theupstream direction to the signaling proxy 325. When the proxy 325receives the first such packet for a given session (for which it hasmade an entry in its local cache), it may append to the packetadditional information such as the sustainable rate and, possibly, otherfeedback parameters for the session that it has received from the RNC330, and forwards the packet toward the server 315. From this point on,the proxy 325 sends an RTCP feedback report to the server 315 at regularintervals. Recall that this interval is typically much shorter (e.g. inorder of hundreds of milliseconds to allow both enough averaging andfast feedback—around 100 ms) than the interval at which the client 310sends its RTCP reports. If the proxy 325 has received a client report(forwarded to it by the GGSN 320) since its last transmission of an RTCPreport to the server 310, the proxy 325 may include the data reported bythe client 310 as well as the feedback provided by the RNC 330 in itsnext RTCP report to the server. Otherwise, the client 310 includes onlythe RNC feedback data in its report to the server 315.

When the server 315 receives an RTCP report from the proxy 325, theserver 315 sets its transmission (streaming) rate equal to thesustainable rate indicated in the report. Typically, the server 315maintains an estimate of the client's buffer level, and, based on thisestimate, makes decisions to increase the encoding rate, decrease theencoding rate or stay at the same encoding rate. That is, the server 315decides whether a higher video encoding rate, a lower video encodingrate or the same video encoding rate should be used for subsequentframes. If the proxy report includes the amount of data currentlybuffered at the RNC 330, the server 325 can use this information torefine its estimate of the content level in its client buffer model.These refined estimates help the server 325 make timely (encoding) ratechange decisions, avoiding potential re-buffering events whilemaintaining a high video quality at the client receiver. Note that usingthe additional information in the reports to refine the content level ofthe client buffer model does not alter the essence of the logic used inmaking (encoding) rate-change decisions.

The server 315 may also send periodic server reports to the client 310,e.g., in RTCP packets. When these packets reach the GGSN 320, they, too,are forwarded to the signaling proxy 325. The proxy 325 records relevantinformation in these packets before forwarding them to the client 310.If the rate at which these reports are sent by the server 325 is higherthan the rate at which the client 310 expects to receive them, the proxy325 may drop some of these reports to ensure that the client 310receives them at a rate consistent with what it expects. In this case,the proxy may have to modify the contents of the server reports itforwards to the client 310 in order to report server statistics at arate which is consistent with the expectations of the client 310. Thisflow of control packets may continue until the client 310 and/or theserver 315 begins the teardown phase with the appropriate RTSP message.When the teardown phase ends, the proxy 325 instructs the RNC 330 tostop sending periodic feedback for the corresponding session. The RNC330 complies with the instruction, and, ultimately, the correspondingPDP context, RAB and radio bearer are torn down.

Embodiments of the techniques described herein may provide a number ofadvantages over conventional practice. For example, in existing videoservice setups, the video server estimates the sustainable rate usingthe data provided by the client. This estimation, being indirect, oftencontains significant errors or may simply be obsolete, especially indynamic operating conditions such as those typical of wireless networks.On the other hand, the sustainable rate determined by the signalingproxy may be more accurate at least in part because it is based ondirect measurements. Improving the accuracy of the sustainable rateestimation allows the server to transmit data optimally, reducing thelikelihood of packet losses in the access network or of underutilizingavailable resources.

Furthermore, in existing set-ups, because of the limited uplinkbandwidth available on the wireless access network, the frequency atwhich the client sends feedback to video server is rather low. Forinstance, in RTP/RTCP-based video streaming sessions, it is typical forthe client to send a (feedback) report to the server once every 5seconds or so. Since there are no such bandwidth limitations between theproxy and the video server, the proxy can send control packets carryingthe currently sustainable rate (and, possibly, other useful bits ofinformation) much more frequently, e.g., once every 100 ms or so. Thiswill help the server to modulate the transmit rate optimally, thus fullyutilizing the network resources without running the risk of losingpackets. The clients can generate their reports at rates consistent withthe capability of the wireless access medium. The proxy will use thesereports to update its knowledge of the client state. The reportsgenerated by proxy (at much shorter intervals) and sent to the serverwill include information derived from the client reports as well as theproxy's estimate of the currently sustainable rate. Such an arrangementmay insure that the client operation is unaffected by the presence ofthe signaling proxy, so no implementation changes are required on themedia client.

Another advantage is that the techniques described herein may allowmedia servers to use estimated sustainable rates that are determined andconveyed to the server by the signaling proxy. In existing set-ups, themedia server uses the information received from client reports to obtainan estimate of the currently sustainable rate. (E.g., via the TCPFriendly Rate Computation algorithm specified in IETF RFC 3448.) Thus,media streaming servers can simply use the periodically-receivedsustainable rate feedback from the proxy in place of the streaming ratevalues that are computed by the streaming server in accordance with theexisting state-of-the-art. The rest of the server functions, inparticular the logic for switching to different encoding rates, mayremain unchanged. The only capability required at the media server is tobe able to operate at a streaming or transmission rate based onsustainable rate prediction provided by the proxy. It is expected thatthis capability will not have any major implication on the serverimplementation. The existing mechanisms for client feedback (e.g. RTCPreceiver reports) can be augmented with simple extensions to carry thesustainable rate feedback and other relevant parameters (if they are tobe reported) from the proxy.

Yet another advantage of the techniques described herein is that theyenable differential treatment to different sessions (streaming as wellas other types) based on such parameters as level of congestion andrelative priorities, and allow the applications to adapt to theprevailing conditions in a flexible and graceful manner. For instance,if the downlink is congested, the signaling proxy can lower the reportedsustainable rate for low priority applications, thus forcing thecorresponding servers to stream at low rates.

The particular embodiments disclosed above are illustrative only, as theinvention may be modified and practiced in different but equivalentmanners apparent to those skilled in the art having the benefit of theteachings herein. Furthermore, no limitations are intended to thedetails of construction or design herein shown, other than as describedin the claims below. It is therefore evident that the particularembodiments disclosed above may be altered or modified and all suchvariations are considered within the scope of the invention.Accordingly, the protection sought herein is as set forth in the claimsbelow.

1. A method, comprising: accessing, at a signaling proxy, firstinformation indicative of at least one state of at least one mediaclient, wherein the first information is received by the signaling proxyfrom said at least one media client at a first rate; accessing, at thesignaling proxy, second information indicative of resources associatedwith at least one air interface, wherein the second information isreceived by the signaling proxy from a wireless network at a second ratethat is at least an order of magnitude higher than the first rate;providing at least one feedback parameter from the signaling proxy to amedia server at a third rate that is higher than the first rate, whereinsaid at least one feedback parameter is formed based on the first andsecond information.
 2. The method of claim 1, wherein accessing thefirst information comprises accessing first information indicative of atleast one of a packet delivery rate to said at least one media client, apacket loss rate associated with said at least one media client,available buffer space in said at least one media client, and anexpected time for buffer overflow or underflow in said at least onemedia client.
 3. The method of claim 1, wherein accessing the firstinformation comprises accessing first information included in at leastone of a plurality of control packets provided by said at least onemedia client at the first rate.
 4. The method of claim 1, whereinaccessing the second information comprises accessing second informationindicative of at least one of a number of users sharing the downlinkbandwidth of said at least one air interface associated with said atleast one media client and a fraction of bandwidth of said at least oneair interface available to each of said at least one media client. 5.The method of claim 1, wherein accessing the second informationcomprises accessing the second information provided periodically or inresponse to a trigger.
 6. The method of claim 5, wherein accessing thesecond information in response to the trigger comprises accessing thesecond information provided in response to at least one of a change in aquality metric associated with said at least one air interface, a signalto interference plus noise ratio falling or rising relative to athreshold, a packet error rate falling or rising relative to a secondthreshold, or a change in a buffer level.
 7. The method of claim 1,comprising forming, at the signaling proxy, said at least one feedbackparameter based on the first and second information.
 8. The method ofclaim 7, wherein forming said at least one feedback parameter comprisesforming information indicative of at least one of a maximum rateavailable to said at least one media client, an amount of data belongingto said at least one media client that is buffered in at least oneentity in the wireless network, a number of packets associated with eachof said at least one media client that were delivered over at least oneprevious feedback interval, and contents of at least one control packetprovided by said at least one media client.
 9. The method of claim 1,wherein providing said at least one feedback parameter comprisesproviding a plurality of control packets to the media server at thethird rate, the third rate being comparable to the second rate.
 10. Themethod of claim 1, wherein the second information is received by thesignaling proxy from a wireless network at a second rate that isdetermined based upon a rate of fluctuations in channel qualityassociated with the air interface.
 11. The method of claim 1, whereinthe first rate is approximately one every 3-5 seconds and wherein thesecond rate is approximately 1 per hundred milliseconds.
 12. A method,comprising: receiving feedback parameters from a signaling proxy at amedia server at a first rate, wherein said at least one feedbackparameter is formed by the signaling proxy based on first informationindicative of at least one state of at least one media client, whereinthe first information is received by the signaling proxy from said atleast one media client at a second rate, and second informationindicative of resources associated with said at least one air interface,wherein the second information is received by the signaling proxy fromthe wireless network at a third-rate that is at least an order ofmagnitude higher than the second rate; and providing, from the mediaserver, at least one packet at a transmission rate determined based onsaid at least one feedback parameter received from the signaling proxy.13. The method of claim 12, wherein receiving the feedback parametersformed based on the first information comprises receiving the feedbackparameters formed based on first information indicative of at least oneof a packet delivery rate to said at least one media client, a packetloss rate associated with said at least one media client, availablebuffer space in said at least one media client, and an expected time forbuffer overflow or underflow in said at least one media client.
 14. Themethod of claim 12, wherein receiving the feedback parameters formedbased on the second information comprises receiving the feedbackparameters formed based on second information indicative of at least oneof a number of users sharing the downlink bandwidth of said at least oneair interface associated with said at least one media client and afraction of bandwidth of said at least one air interface available toeach of said at least one media client.
 15. The method of claim 12,wherein receiving the feedback parameters comprises receivinginformation indicative of at least one of a maximum rate associated withthe wireless network, an amount of data belonging to said at least onemedia client that is buffered in at least one entity in the wirelessnetwork, a number of packets associated with each of said at least onemedia client that were delivered over at least one previous feedbackinterval, a time-stamp or sequence number associated with the lastpacket delivered to said at least one media client, and contents of atleast one control packet provided by said at least one media client. 16.The method of claim 12, wherein receiving the feedback parameterscomprises receiving control packets at the media server at the firstrate.
 17. The method of claim 12, wherein providing said at least onepacket comprises applying rate shaping to at least one variable bit ratedata stream in accordance with the determined transmission rate.
 18. Themethod of claim 12, wherein the second information is received by thesignaling proxy from a wireless network at a second rate that isdetermined based upon a rate of fluctuations in channel qualityassociated with the air interface.
 19. The method of claim 12, whereinthe second rate is approximately one every 3-5 seconds and wherein thethird rate is approximately 1 per hundred milliseconds.